Improve look of tabs when using a layout other than top (#3925)

src/widgets/helper/NotebookTab.hpp

@@ -2,6 +2,7 @@
 
 #include "common/Common.hpp"
 #include "widgets/BaseWidget.hpp"
+#include "widgets/Notebook.hpp"
 #include "widgets/helper/Button.hpp"
 
 #include <QMenu>
@@ -40,6 +41,7 @@ public:
     void setSelected(bool value);
 
     void setInLastRow(bool value);
+    void setTabLocation(NotebookTabLocation location);
 
     void setLive(bool isLive);
     void setHighlightState(HighlightState style);
@@ -94,6 +96,7 @@ private:
     bool mouseDownX_{};
     bool isInLastRow_{};
     int mouseWheelDelta_ = 0;
+    NotebookTabLocation tabLocation_ = NotebookTabLocation::Top;
 
     HighlightState highlightState_ = HighlightState::None;
     bool highlightEnabled_ = true;